1. Field of the Invention
The present invention relates to premix and foaming compositions for a polyurethane foam.
2. Description of the Related Art
A polyurethane foam is an important material for industrial and civilian fields, and is widely used in furnishing, packaging, textile, and insulating materials. Typically, the polyurethane foam is formed by polymerization of diisocyanate, polyol and a chain extender, e.g., diol or diamine compounds. The drawbacks of the polyurethane foam include insufficient hydrolytic stability, deterioration and yellowing under high humidity, high temperatures and UV light exposure.
TW Publication Application No. 200823242 discloses a formulation of a non-yellowing polyurethane foam made by first preparing a prepolymer that includes at least one aliphatic isocyanate and at least one polyol, followed by addition of other additives such as a crosslinking agent, a surfactant, a catalyst, a blowing agent and water in the prepolymer to undergo emulsification and foaming reaction. However, the blowing agent used is a volatile organic solvent, such as pentane and dichloromethane, which poses harm to both humans and the environment.
US Publication Application No. 2009/0253821 A1 discloses a polyurethane foam with water absorbency and yellowing resistance. The polyurethane foam is obtained by reacting a polyester polyol, an alicyclic polyisocyanate, a water-absorbency-imparting agent, a catalyst and a blowing agent. However, since the water-absorbency-imparting agent enhances the hydrophilic property of the foam, the moisture retained in the foam might result in hydrolytic instability. In addition, the polyester polyol disclosed in the US publication is in a solid state or a liquid state with high viscosity. This requires heating or addition of solvents during a pretreatment step, and is thus less convenient to use.
WO2007/142425 A1 discloses a process for preparing a polyurethane foam with yellowing resistance via the reaction of (di)isocyanate with polyether polyol. In the PCT publication, the yellowing resistance effect of the foam is achieved by addition of a polyvinyl compound in polyether polyol, i.e., polyether polyol B. That is, in the PCT publication, the used polyether polyol per se cannot provide anti-yellowing property.